A known method of recovering erroneous information in a radio or wireless communication system is to request the re-transmission of erroneous data packets by acknowledging the successful or unsuccessful reception of each packet in a return transmission to the originator of the data packets. The return transmission contains explicit or implicit information about each of the received data packets and initiates a retransmission of the erroneous packets to the message recipient. This known method of recovering erroneous message data is known as an automatic repeat request (ARQ) protocol. Two examples of ARQ protocols are "selective repeat", in which only specific, erroneous data fragments are re-transmitted, and "go back n", which initiates a retransmission of all data fragments starting from the first incorrect fragment. Known ARQ methods require that both the sender and the recipient of the message data have equal transmission capability and operate independently of each other, exchanging message data and response information until the entire message has been processed. Disadvantageously, these known ARQ methods are not designed to operate on systems where the system control is one-sided, such as in a two-way paging system. In a two-way wireless selective call, or paging, system, a system controller at a fixed paging terminal is responsible for scheduling all of the transmissions for the selective call transceivers, including dictating when any ALOHA-style transmission can be made by a two-way pager, or transceiver. A typical two-way paging system, with limited reverse channel (i.e., transmission from two-way pager to paging system) messaging capability, requires that the portable selective call transceivers, transmit only when commanded to do so by the system controller.
Portable pagers, or selective call transceivers, operating in such a system, are limited in memory, processing power and, as a result of dependence upon limited battery power, the ability to perform numerous continuous transmissions. Since known ARQ methods require the capability to independently initiate and control transmissions from both the sender and recipient of message data, selective call transceivers are not able to support the transmission requirements necessary to complete ARQ transactions using known methods. Known ARQ methods require data storage, processing and transmission requirements beyond the capabilities of selective call transceivers. These limitations in the selective call transceivers make known ARQ methods unsuitable for use in a two-way paging system with limited inbound messaging capability where the transmission scheduling is provided solely by the system controller.
Known paging systems also lack the capability of efficiently assigning a plurality of two-way pagers to transmit during a same time slot because known systems either lack sufficient information about the location of the plurality of two-way pagers, or lack the capability to dictate that more than one two-way pager transmit at the same time, or lack both.
Thus what is needed is a message acknowledgment method and apparatus that requests automatic repeat of missing or erroneous information recovered from a radio signal from a selective call transceiver received at a paging system terminal via a reverse channel that minimizes delay caused by acknowledgments and that consumes minimal forward channel capacity.